Electromagnetic tachometer.



.N. M. HOPKINS, ELEOTBOMAGNETIO TAOHOMETER.

APPLICATION FILED AUG. 1, 1912.

Patented Nov. 11, 1913.

6 SHEETS-SHEET 1.

N. M. HOPKINS.

ELECTROMAGNETIC TAGHOMETER.

APPLICATION FILED AUG. 1, 1912.

Pat ented Nov, 11, 1913.

5 SHEETS-SHEET 2.

N. M. HOPKINS.

ELECTROMAGNETIC TAGHOMETER.

APPLICATION FILED AUG. 1, 1912.

6 SHEETSSHEET 3.

1,078,200, Patented Nov. 11, 1913.

wane/@635.- Inuenlor; TVQW MM w. 62

11. M. HOPKINS. ELECTROMAGNETIC TAGHOMETER.

APPLICATION FILED AUG.1, 1912.

1,078,200, Patented Nov. 11, 1913.

5 SHEETSSHBBT\4.

N. M. HOPKINS.

ELEGTROMAGNETIG TAGHOMETER.

APPLICATION FILED AUG.1, 1912.

1,078,200. I Patented Nov. 11, 1913.

5 SHEETS-SHEET 5,

UNITED rec JMBIA, nsstenon, n2"

any, or EHXLADEL- PHIA, PENNSYLVANIA, A COEEQTMTION 331w Z ELECTROMAGNETIC TACHQMETEIR.

Specification of Letters ented Now. i L, 15313..

Application filed August 1,1912. Serial Hal 712,738.

current drivenby the wheel or shaft whose;

speed is to be measured.

In the accompanying drawings,Fignre 1 is a plan view of the meter proper; ig. 2 is a plan view of the meter, with a. portion of itscover and dial broken away; Fig. 3 is a section of the'rneter, on the line Ill-TH of Fig. 4; Fig. 4 is a sectional side elevation of the meter, on the line IVIV of Fig. 3; Fig. 5 is a detail View of a meterpointer adjusting-device; Fig. 6 is a detail view of a meter hairspring connection; Fig. 7 is a detail view of a meter rotor-ferrule; F ig. 8 is an end elevation of an automobile type of magnet-o generator, with the driving-pinion and one end-plate removed; Fig. 9 is a side elevation of this generator, itscase being shown in vertical section;

10 is a diagrammatic view of an automobile tachometer with a battery-energized odometer; Fig. 11 is a wiring diagram of a tachometer, shdwing automatic and non automatic reactances for temperature-cornpensation and for calibration; Fig. 12 is a vertical transverse section of an engine-room type of magnets generator, on the line XII-XII of Fig. 13; and Fig. 13 is a vertical axial section o-fthis generator.

The indicating instrument, or meter proper, A, illustrated in Figs. 1 to l, prises a cylindrical water and dust-probcase 1, having a dial 2 with a speedscale 3, over which plays a pointer The meter has an electromagnetic system consist-- ingot a series of superposed rings 5 of sort sheet-iron, from which extend radially in ward fourinte raloleieces 6. Each' ole- I p F )iece carries a Winding 7 the tear windlngs are connected to receive. two-phase rent from a magneto generator. Fixed within and a gacent to the pole-pieces is a cylindrical soft-iron core or armature 8, having a central passage which receives a spindle 9, jonrnaled at its ends in jeweled bearings 10. The rotor 11, an inverted cup of aluminum having a soft-iron lining 12, is concentrically secured on shaft 9 by a twopart ferrule 13, 13, shown in detail in Fig. 7. This ferrule has an internal spiral groovel-i, and is soldered to the rotor 11 and spindle 9, the solder flowing downward into the groove 1 The rotor and its pointer d are held in the Zero position by a hairspring 15, the inner end 16 of which is secured by solder 17 to a clip 18 fixed on the spindle 9, as illustrated in Fig. 6. Clip 18 has fork 18 which receives and closely fits the hair-spring, a point somedistance from its soldered end 16, where 'the elasticity has not been impaired by the heat used in applying the solder. The other end of spring 15 is secured to a lug 19 depending from thin concave radially-slotted centrallyertured spring-disk 20. This disk is r'evolubly mounted on and is held under slight tension by a fiangednut 21 threaded on the upper pivot-jewel screw 10. Disk 29 has an arm 22 which engages a depending for on the e1 d of a bell-crank lever 24- mounted on a pivot 25. The other arm 26 of this lever is bent downward and has a vertical slot 26, shown in '5, which receives a pin 2? projecting from a. revoluble disk 28 carried-b a pivot 29 journaled in the side-wall of the meter-case 1. The outer end of this pivot is slotted to receive a screw-driver. A. spring-washer 30 is interposed between the disk 28 and the case, offering frictioresistance to'the rotation of the llSlZ. in; v,urning; the disk 28, the position the lever and thereby of the l a d outer end of the hairested, to set the pointer zero on scale 3.

icurrent is supplied to 7 7 of the electromagnet,

electromagnetic field thereby produced turns the rotor 11 and pointer lthrough an dependent on the strength and frequency of the current flowing. The variah le torque of the rotor, opposed by that .plate 79, intermediate the magnets.

ten core 64; The ends sees es, and

outer end? 1 being 'fixed to the "3'2 rece-iving the upper pivot 69. The coiled s p 70, unwinding or rewinding 3e tei ture of the atmosphere about it' changes, shifts the-position of the flux-carrier oTa'n-d correspondingly varies the 'rea'ct'ance of coil 65. As the temperature'falls and thereby increases the conductivity of the copper circuit-wires 62, meter-windings 7' and erator-win'ding43 of one phase, and that of the aluminum rotor, the thermostat acts increase the reactance of wit @5, and reversely, decreases its reactance' as the tem; perature rises. A non-automaticcompensator, comprising a-reactance coil 73 a manually-adjustable core=74 is also interposed in circuit 62, serving to: the initial calibration of the'meter, set to interpose such reactan-ce-as to compensate at the temperature of calibration. Similar automatic and non-automatic reaetance compensators D, E are interposed in the circuit 62 connecting the meter-winding '7 and generator-winding 42 of the other phase;

The engine-room type of magneto generator illustrated in Figs. 12, 13 comprises two heavy horseshoe magnets-7 5, arranged side by side but spaced apart. The ends of these magnets are seated in rabbets in the baseplate 76. A sheath 77 of spring-brass surrounds and clamps the magnets, its ends being secured to the base-plate by screws 78. A rectangular soft-iron plate 79 is clamped against the inner faces of the corresponding polar extremities of the magnets, by a bar 80 bearing ag inst their outer faces and having a screw 81 which enters}: projection on Plate 79 has two integral rectangular soft-iron extensions, with concave faces, serving as polepieces. One of these extensions, 82, has a winding 83, and theother has a winding 84. A rectangular soft-iron plate 85 is similarly clamped against the inner faces of the opposite polar'extremities of the magnets, and has a single long unwound extension and pole-piece 86'. Revolubly mounted-between the two wound and the unwound polepiecesare two rigidly-connected soft-iron inductors 87, 88 having trunnions 89, 90 which-are journaled in end-plates 91, 92. WVhen these rotors are driven'by the shaft whose speed is to be measured, two-phase circuit.

clescrib like th no t 1 86 in th .temobiie to he i s through the particw e space between the poie-pieces. W) from. external generator is inco-rnprising bot wPdLS 95. An autourew mpensat r B, of the i he etofore described, is mount-- in the case. i ihere; as on b is tieshins, t e meter and generator are located at diiier at points which may be at widely different temperatures, the meter for era i g on the bridge while the generator is to enipioy two automatic compensators' D, D, one in the i- Later-case, as shown in. Fig. 3, and the other in the generator case. One OfthfiSE comper tors may be placed in each phase oilo, as show in Fig. 11. In the two-phase oinolnie tachometer, it is sutiiprovide an automatic compensator nase circuit and a' non-automatic calibrating compensatorin the other phase The reactance coils not only serve as temperature-compensators, but also. assist in maintaining a uniform ratio between the generatonspeed and meter-rotor torque, the reactance increasing" with the speed, frequency and generated electromotive force,

thereby con'ducing to uniformity of scaledivisions;

One or the other of the two inductors 44, 45, or 87, 88, of bothtypes of generator, at all times acts as a magnetic bridge or arma ture for alt otthe assembled-magnets, the combined iiux of which is carried by softiron rivets 36 or plates 79, whereby the re tention of their magnetism is insured.

The multiplying gears 50, 51 drive the inductors 44, 45 at a higher speed than that of the shaft 52. Such high inductor-speed is important, giving currents of high frequency, thereby improving the reading on the lower part of the meter-scale.

Theinductors being journaled in internal dust proot bearings, which are little subject to wear, may be of such size as to nearly fill the gap between the magnet-poles, thereby giving a magnetic circuit of low resistance."

The expression continuous and permanent circuits, used in certain claims, is intended to distinguish from circuits including slip-rings with brushes bearing thereon, which introduce an objectionable and-variable resistanes, impairing the accuracy of the readings.

Structural'teatm'es of the meter and generator shown herein are claimed in my apin the engine-room, itis preferable egg indicator member, i1 s measured: a pluraiity of adjusts &

2. In a tachometer consisting o: i cator member, a Winding or Win adapted to receive electric current actuate said indicator member, and if Q plying alternating electric current to said Winding or windings, including member driven by the Wheel or Whose speed is to be measured: an adjustahie reactance in the tachometer circuit, adapted to com.- pensate temperature-changes esistance ChElilD, Without varying the ohmic circhit-resistance,

l'n tachometer consistin ndicator member, s Winding or W1 ed to receive electric current 2 indicator member, and means ernating electric curren i no; or Win" '15, including a me hr i a tachometer consisting o l 1 A we n V -1 7 said 1nd LO; member, and means 0;; s

I- M .L L A i pi m alreinatlng elec c CUZTEZL to said eluding a Jmemoer driven by the men or sin t Whose speed is to he rrieasure a plurality or reactances in the tachoz cuits, at points suhj diii eren hire-conditions, adapted to conipe os perature-changes of resistance Without varying the ohmic circuiti'esistance.

5. in a tachometer consisting of ind cator member, a Winding -windings ada tto to receive electric current and actuate saie.

n for supnlvin alternating electric current to or windings, including a member a I the wheel or she-ft Whose speed is to Winding or Wi ancesin the tachometer circuit or and a thermostat contr lling one or saic re actances.

ln-a tachometer con noting-current in .ter 1? connecting leads: a plurality of thermostatically-controiled reactances in the tachometer circuits, one of said reactances being adjacent to meter and the other to said generator,

7., a tachometer consisting of a polyfiase meter and generator and connecting leads: an adjustable rcactance in each phase circuit of said tachometer, adapted to compensate temperaturechangcs or" resistance therein Without Varying the ohmic circuitresistance,

In a tachometer consisting; of a poly -se meter and generator and connecting i statically-controlled reactarise in each phase circuit of saidtachomo, A tachometer consisting oi; an altern ting-cnrrent generator and meter and connecting leads, said generator comprising a permanent tield-magnet With a Wound pole-piece and an inductor member, and said meter comprising ficldcoiis and an indicator member, the Wine ll gs of said generator and meter and said leads constituting coiitlriuons and permanent circuits.

F.- E; tachometer consisting of a polyphase generator and meter and connecting leads, erator comprising a perinancnt fields set with wound oolopieces d inductors respectively opposed to said pole-pieces, and said meter comprising fieldthe windings of :icator rotor,

"L said leads con- ;-uous and permanent cirsing a perina- :-t with We id pole-pieces l inductors "pcctively opposed to a pole-pieces, and said meter comprising field-coils, a hollow indicator r tor, and a soft-iron core within s: 'd rotor, the windings osaid generator and meter and said leads constituting continuous and nermanent circuits,

19. A tachometer consisti -T-; of a poly- -l.ase generator and meter aiid connecting eads, said generator comprising a permanent field-magnet with superposed parallel Wound pole-pieces, and superposed inductors relatively oii'set at an angle of 4-5 respectively opposed to said pole-pieces, and said meter comprising an electromagnct Wound to provide poles spaced apart 98, and! an indicator rotor, 11 1e windings oi said generator and meter and said leads constituting continuous and permanent circuits.

tachometer consisting of an alter- :iating-curren .crator and meter and connecting leads, said gene ator comprising 1 'w'aterand, dust'prooi case, a wound oor- =*".Hil n a 1st, revoluh e 111 motor momcase, multgmlying within said case, connecting sai s a 'and inductor member,

whereby the, inductor-speed. is such as to give currents of comparatively high voltage and frequency, said meter having a comparatively' uniformly-divided scale.

14. A tachometer consisting of an alternating-current generator and meter and connecting leads, said generator comprising.

a waterand dust-proof case, a wound permanent magnet, a revoluble inductor member, a driving-shaft extending throu h said case, and multiplyin .gearswithin said case, connecting said sha t and inductor member, whereby the inductor-speed is such as to give currents of comparatively high voltage and frequency, said meter havin a 'comparatively uniformly-divided sca e, and a.

reactance in the tachometer circuit, adjusted to contribute'to the uniformity of the meter- I,

scale divisions;

'15.- A tachometer consisting of an alternating-current generator and meter and connecting leads, the winding: of Slld meter and generator and said leads constituting "continuous and permanent circuits, said generator comprlsmga waterand 1 dustproof case, a wound permanent magnet, a revoluble inductor member, a driving-shaft extending through said case, and multlplyf ing gears within said case, connectlng sa1d shaft and inductor member, whereby the inductor-speed is such as to give currents of EUGENE A. BYnNas.

comparatively high voltage and frequency, and .said meter having a comparatively un1- 

